<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width,user-scalable=no,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0">
    <title>Title</title>
    <style>

        body{
            margin: 0;
            padding: 0;
        }
        .app{
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);
            /*margin: 0 auto;*/
            height: 200px;
            width: 200px;
            border: 1px red solid;
        }
    </style>

</head>
<body>

<!--200*200 盒子上下左右居中，在任何的分别率中-->


<div class="app"></div>
</body>
</html>
